1. Technical Field
This invention relates to inhalation devices for use with metered-dose aerosol canisters in inhalation therapy. In another aspect, this invention relates to inhalation devices that increase the fraction of drug that can be delivered in respirable form from an aerosol canister. In yet another aspect, this invention relates to inhalation devices that retain non-respirable particles. This invention further relates to methods of administering pharmaceutical formulations via inhalation therapy.
2. Description of the Related Art
It is often desirable to increase the fraction of drug in an aerosol formulation that can be delivered from an aerosol canister in respirable form. Various deagglomeration units are known to the art and are said to be useful for such a purpose. Also, geometry has been modified in order to improve the performance of aerosol actuators for use in inhalation therapy. For example, U.S. Pat. No. 2,865,370 (Gattone) describes a dispersing adaptor for use with disposable aerosol units wherein the container discharges against a curved surface Similarly, U.S. Pat. No. 4,940,051 (Lankinen) describes an inhalation device involving a curved baffle plate which deflects the aerosol discharge into an inhalation chamber. Generally spherical chambers and curved surfaces have found use in other aerosol applications. For example, U.S. Pat. No. 2,585,429 (Boe) describes an atomizing nozzle for use with liquified gases. The nozzle involves tertiary expansion of the gas from a storage container and is said to produce satisfactory fine sprays even when the liquified gas is maintained in the storage container at pressures as low as 20 psig. Primary expansion occurs in a chamber which can be generally spherical and wherein eddy currents tend to break up liquid droplets Secondary expansion occurs in a chamber that can be formed at an angle of 30.degree. to 60.degree. to the longitudinal axis of the primary expansion chamber. Tertiary expansion is into the atmosphere.